Immunization FAQ

Learn how immunizations work to fight communicable diseases on both the individual and community levels, and why it’s important to keep current with recommended immunizations.

What are immunizations?
Also known as vaccines, immunizations are made of biological substances, including antigens — substances that the body recognizes as foreign or toxic.

Immunizations increase the body’s resistance to a particular disease. Doctors administer immunizations, usually in the form of shots, to protect us from developing diseases like polio, pertussis (whooping cough), measles, mumps, chickenpox and many others.

Why is it important for everyone to receive immunizations?
Widespread immunizations help develop what’s called “herd” or “community” immunity. These terms refer to protection against disease that extends to an entire population, once most of that population has received a given immunization.

Why continue immunizing against rare diseases?
According to the Center for Disease Control, it’s important to keep immunizing even when a disease has been mostly eliminated — because just a few cases of that disease can infect an unimmunized population and undo years of progress made by consistent, widespread immunization.

Are immunizations safe?
Data from the CDC indicates that the United States currently has the safest, most effective supply of vaccines in history. The most common reactions to immunizations include soreness at the injection site, fever and fatigue.

How are immunizations scheduled?
Children can receive as many as 14 immunizations at once by the time they are 2 years old, according to the American Academy of Pediatrics. Some of these can be administered in the same shot, lessening the necessary number of needle pricks.

Though parents may worry that simultaneous vaccines may overwhelm their child’s immune system, this situation is unlikely. Children’s immune systems routinely fight off up to 6,000 antigens per day, according to the American Academy of Pediatrics; by contrast, the current schedule of recommended immunizations for kids includes a total of 150 antigens.

Why should I talk to my doctor about immunizations?
Some children or adults should not receive certain immunizations: for example, in the case of allergies or a compromised immune system. Providing a complete medical history to your health care providers will help them determine which immunizations are right for you.

Protection against disease begins at the cellular level — that’s why it’s important to make sure that you and your family are up-to-date on recommended immunizations.

Visit cdc.gov to learn more and to view schedules of immunizations for young children, teenagers and adults.